Roadbed on which electrically powered vehicles can be operated

ABSTRACT

A system for controlling wheeled vehicles on a track. The system provides for simultaneous remote control of a number of vehicles which receive both power and control signals from conducting elements on a track so configured as to receive the signals from a remote controller. The system allows unlimited steerability of the vehicles, continuous and smooth speed control, and dynamic braking and reversing of the vehicles. A roadbed for use in the system is disclosed.

United States Patent Reynolds et al.

[ 5] Oct. 15, 1974 ROADBED ON WHICH ELECTRICALLY POWERED VEHICLES CAN BEOPERATED Inventors: Robert J. Reynolds, 1543 Pine Valley, Ann Arbor,Mich. 48104; Herman F. Deyerl, PO. Box 3721, Santa Monica, Calif. 90403Filed: Feb. 14, 1973 Appl. No.: 332,309

Related US. Application Data Division of Ser. No. 184,105, Sept. 27,1971, Pat. No. 3,736,484.

US. Cl. 238/10 E, 46/1 K, 104/148 LM, 191/2 Int. Cl A63h 18/12 Field ofSearch 238/10 A-lO E, 238/10 F; 104/60, 148 LA, 149; 46/1 K; 191/22, 2

References Cited UNITED STATES PATENTS 9/1955 Seyffer 104/149 2,872,8792/1959 Vierling 104/149 2,965,044 12/1960 Johnson, Jr....... 104/1493,288,368 11/1966 Athearn 238/10 F 3,460,287 8/1969 Arnow 104/1193,729,133 4/1973 Covert 238/10 E Primary ExaminerM. Henson Wood, Jr.Assistant Examiner-Richard A. Bertsch Attorney, Agent, or FirmOlsen andStephenson A system for controlling wheeled vehicles on a track. Thesystem provides for simultaneous remote control of a number of vehicleswhich receive both power and control signals from conducting elements ona track so configured as to receive the signals from a remotecontroller. The system allows unlimited steerability of the vehicles,continuous and smooth speed control, and dynamic braking and reversingof the vehicles. A roadbed for use in the system is disclosed.

ABSTRACT 3 Claims, 20 Drawing Figures PATEMEBBE? 1 51974 SHEET 1 0f 4ROADBED ON WHICH ELECTRICALLY POWERED VEHICLES CAN BE OPERATED REFERENCETO RELATED APPLICATION This is a divisional application of applicationSer. No. 184,105, filed Sept. 27, 1971 entitled A System for OperatingElectrically Powered Vehicles on a Roadbed, now U.S. Pat. No. 3,736,484.

BACKGROUND OF THE INVENTION The present invention relates toimprovements in a roadbed for electrically powered toy vehicles adaptedfor travel on the roadbed.

Remotely controlled toy cars have been previously known. Former systemshave been generally of two types. The first type conventionally employeda slot, groove or other similar steering device which constrained thecar to a fixed path with speed control being the only function remotelycontrollable. The second type provided for remote control of bothsteering and speed. Some systems in this second group require the use ofa battery in the vehiclefor propelling power while control is performedremotely. Other systems that supply both power and control from a remotesource of supply to a track have failed to operate satisfactorily forvarious reasons, and the present invention is directed toward overcomingthe shortcomings of such other systems.

One such system is disclosed in U.S. Pat. No. 3,205,618 to Heytow, whichshows an integrated system for control of speed and steering as well asproviding power externally to the vehicle. Systems of this type sufferdrawbacks in operation relating to unlimited steerability, the number ofvehicles that may be oper ated simultaneously, and continuousessentially linear speed control. The present invention overcomes theseproblems while providing a system that is realistic in play-action andperformance and practical in terms of manufacture, and in particularprovides an improved roadbed for use in the system.

SUMMARY OF THE INVENTION The invention includes a roadbed capable ofreceiving superimposed A.C. or DC. signals from an external controller,which can be used in combination with a wheeled vehicle of the typedisclosed in U.S. Pat. No. 3,590,526, issued July 6, 1971 for RemotelySteerable Vehicle," that in turn receives power and control signals fromthe track through a minimum number of contacts, has circuitry toreceive, detect and respond to those signals, and has electro-mechanicaltransducers, generally DC. motors, to propel and steer the vehicle.

The roadbed may have one of several shapes; for example, that of aone-piece rectangular surface. How ever. a roadbed in the form of atrack approximately oval shaped is the most familiar course employed forthe competitive racing of more than one vehicle. There are two types ofsections from which the track is formed, a straight section and a curvedsection. In reference to the conductive track surface, a preferreddesign permits the interchange of, respectively, any straight sectionsand any curved sections, which facilitates the assembly of the track.The contacts on the vehicle are geometrically spaced so that a minimumnumber will assure that at least two will be contacting oppositepolarity conductingsegments on the track for all orientations of thevehicle. The spacing of flexible contacts may be accurately maintainedwith a special guard device. The circuitry allows for the reception ofeither constant frequency or variable frequency control signals. Itsaction provides for the minimization of cross-talk and for compressionof the dynamic range of the remote signal source because of the loadingof that source by the receivir'ig circuitry, both effects facilitatingthe simultaneous independent operation of several vehicles on a commonroadbed. Smooth and precise control of the vehicles is made possiblethrough the provision of a minimum resistive load for the commutatingdiodes which are part of the receiving circuitry in the vehicles, and'byarranging the circuitry in such a way as to utilize the inherentself-regulating characteristics of the drive motors.

Thus, it is among the objects of the present invention to provideimprovements in a roadbed on which electrically powered vehicles can beoperated.

Other objects of this invention will appear in the following descriptionand appended claims, reference being had to the accompanying drawingsforming a part of this specification wherein like reference charactersdesignate corresponding parts in the several views.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a fragmentary plan viewshowing a straight section of the track embodying a portion of thepresent invention;

FIG. 2 is a plan view of a curved section of the track;

FIG. 3 is a plan view in reduced scale of a composite track comprisingten sections (with details of sections excluded);

FIG. 4 illustrates schematically a four contact pickup arrangement ofthe vehicle that can be used on a straight track section;

FIG. 5 illustrates schematically a five contact pickup arrangement ofthe vehicle for use on both curved and straight track sections;

FIG. 6 is a fragmentary side elevational view of the contact guard inits mounted position on the vehicle;

FIG. 7 is a top plan view of the contact guard that is part of a vehicleemploying five contacts;

FIG. 8 is a schematic diagram of the basic receiving circuitry FIG. 9 isa block diagram of the basic receiving circuitry in the vehicle;

FIG. 10 is a graph showing the approximate frequency response curves ofthe frequency filters and their separation with respect to frequency inthe case of constant frequency control of the vehicles;

FIG. 11 is a schematic diagram of the series resonant filters used inthe basic receiving circuit;

FIG. 12a is a diagram showing a theoretically possible assignment ofcontrol frequencies for constant frequency control;

FIG. 12b is a diagram showing a practical assignment of controlfrequencies adapted for constant frequency control;

FIG. is a diagram showing a practical assignment of control frequenciesfor variable frequency control;

FIG. 13 is a frequency graph showing the approxir mate frequencyresponse curves of the slope detectors and their separation with respectto frequency in the case of variable frequency control of the vehicles;

FIG. 14 is a schematic diagram of an alternate detector' circuit, avoltage doubler, for use in the basic receiving circuit;

FIG. is a block diagram showing a circuit modification for the basicreceiving circuit to provide braking and reversing of the vehicles usinga pulse modulation method,

FIG. 16 is a schematic diagram of the pulse modulation circuitmodification used for braking and reversing the vehicle;

FIG. 17 is a block diagram showing another circuit modification for thebasic receiving circuit to provide braking and reversing of the vehicleusing an amplitude modulation method; and

FIG. 18 is a schematic diagram of the amplitude modulation circuitmodification used for braking and reversing the vehicle.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Before explaining the presentinvention in detail, it is to be understood that the invention is notlimited in its application to the details of construction andarrangement of parts illustrated in the accompanying drawings, since theinvention is capable of other embodiments and of being practiced orcarried out in various ways. Also, it is to be understood that thephraseology or terminology employed herein is for the purpose ofdescription and not of limitation.

Referring first to FIGS. 1-3, a brief description of the track whichforms the roadbed will be given. With reference to FIG. 1, a straightsection of the track, generally at 10, shows the configuration ofconductors 11 and 12. Each conductor is a solid, continuous piece ofconducting material formed into uniform segments 13 and 14 extendingrespectively perpendicular from common conductor busses 11a and 12a. Theperpendicular conducting segments 13 and 14 are alternated so that avehicle traveling parallel to the common busses 11a and 12a andperpendicular to the conducting segments 13 and 14 would encounter firstconductor 11 and then conductor 12 and so forth. The space between theconductors 11 and 12 consists of an insulator 15.

Where two sections are joined at a line 16 (FIG. 1), clamps 17 and 18hold the two sections physically together and provide electrical contactbetween conductors 11 of sections A and B and conductors 12 of sectionsA and B.

With reference to FIG. 2, a curved section 20 of the track shows theconfiguration of the conductors l1 and 12 and interposed insulator 15.The conducting segments l3 and 14 of each conductor 11 and 12 extendingradially, vary proportionally in width as the radial distance increases.The section 20 is dimensioned so that it can be joined to a straightsection or another curved section at line 16 with clamps l7 and 18, forexample, similar to the connection used between straight sections 10.

With reference to FIGS. 1 and 2, in the preferred configuration of thestraight and curved track sections, the sections are so dimensioned thatthe last conductor at one end is a segment 13 and at the opposite end asegment 14. Further, the track sections are terminated, exactly alongthe edge of the conductor segment at one end and along the edge of aninsulator 15 at the opposite end and along the edge of an insulator 15at the opposite end. In this way, a uniform, nearly perfect transitionwith respect to the conductor/insulator pattern obtains where adjoiningtrack sections mate. 7

With reference to FIG. 3, one possible configuration of a track 22 usingcurved sections 28-33 and straight sections 24-27 is shown. The track 22forms a closed roadbed. In this configuration conductors 11 and 12 areessentially circular, and electrical current introduced to the track ata point 34 has two parallel paths to travel in conductor 11, oneclockwise and one counterclockwise to reach point 35. Since a conductorhas a characteristic voltage drop dependent on its length, the closedconductor configuration assures that current travels a maximum of onlyone half the length of a closed tracks configuration in order to reachthe farthest point from the input at which a vehicle may be located.This minimizes the characteristic voltage drop and helps maintainaccurate vehicle control regardless of the vehicles position on thetrack with respect to the input.

The pattern of the conducting segments 13 and 14 and the insulator 15determines the number and the geometric arrangement required for theelectrical contacts mounted on the vehicle (not shown) employed to pickup the electrical signals from the track. In order that there be acontinuous flow of current from track conductors 11 and 12 to thevehicles circuitry, there must. be at least one contact in engagementrespectively with each of conducting segments 13 and 14.

To obtain optimum performance of the vehicles on the track it is foundthat certain configurations or arrangements of the contacts on thevehicle are necessary, and procedures that may be followed for arrivingat desirable patterns will next be explained. FIGS. 4 and 5 showschematically two such contact pickup configurations, with contacts41-44 representing a fourpickup pattern in FIG. 4 and contacts 41-45representing a five-pickup pattern in FIG. 5. Dimensions a, b, c and dindicate the proper spacing. Referring back to FIG. 1 dimensions l and Srepresent the width of insulation and conducting segments respectively.

Referring to FIG. 2, dimension R, represents the inside radius of thecurved track section 20 and R the outside radius of the curved tracksection 20 respectively. S, and I, represent the width of the conductingsegment and insulator respectively near the inside diameter, and S andI, represent the width of the conductor segment and insulatorrespectively near the outside diameter of the track. Spacing of contactsis achieved by first considering the rectangular track section 10 ofFIG. I. It is found that a practical fourpickup pattern, FIG. 4, can bespecified as follows:

The exact dimension of 2 c depends on the respective dimensions of a andb and is chosen such that if any one pickup is held in place on any spotof any insulator, e.g., by means of a pin (the pin test), and the pickuppattern is revolved 360 around that point (a rotation of only 180 isrequired in the case of pickups 41 and 42, and it is sufficient to testonly one of pickups 43 and 44, because of symmetry), then there mustalways be at least two pickups contacting segments of opposite polarity.As was already implied, this test must be applied to pickups 41 and 42and 43 or 44. Any one of several patterns that satisfies thisrequirement will be a usable one. (The exact dimensions of the severalpatterns can be specified mathematically, by geometric relationships).

In the case of track sections having curved boundaries 20, the patternof parallel transverse segments of constant width must be modified ifthe transverse segment orientation is to be maintained over the surfaceof the curved sections 20. With a conductive segment pattern as in FIG.2, there is a considerable variation in segment width from the insideboundary (radius R,) to the outside boundary (radius R,), because of therelatively small radii involved in a track of conventional size. Becauseof this varying segment width, the fourpickup arrangement in FIG. 4would not serve to meet the requirement for continuous current flowdefined previously, nor would any other arrangement of four pickups. Theaddition of a fifth pickup will make possible a pickup arrangement thatwill meet the requirement everywhere, on the straight as well as thecurved sections.

As in the case of the four-pickup arrangement, a symmetricaldistribution of the brushes is also the most logical one for thefive-pickup arrangement. The fifth pickup 45 is placed on the line ofsymmetry, below the base line of the isosceles triangle formed by thecontacts 42, 43 and 44 as shown in FIG. 5. In regard to dimensioning ofthe spacing of the pickups, similar considerations apply as thosespecified for the case of the four-pickup arrangement. It happens,however, that the spacing involved with travel on the radial stripsurface is much more critical than that on the parallel segment surfacebecause of the variation in width from one end of the segment to theother: ratios of these widths on the order of 2:1 and larger (dependingon the radii of the curved boundaries) may obtain. It is apparent that acomprehensive mathematical formulation for the pickup spacing is muchmore involved here than in the case of a parallel segment pattern.

In determining a usable five-pickup arrangement, one can at once specifythe dimension 2 c as follows:

a. If the line of symmetry of the pickup pattern is moved along aninsulator towards the inner boundary, then the relationship must obtain,where S, is the inner usable segment width and I, the insulator width atthat point.

b. If the pattern is similarly moved to the outer boundary, but alignedwith the radial bisector of any segment, then the relationship mustobtain, where S, and I, are analogously defined as S, and 1,. Thedimension 2 c, and thus the position of pickups 43 and 44 has beenestablished.

It is possible to determine the spacings a and b for tangential travelat the center of the track (at a distance (R, R )/2, with reference toFIG. 2). The relationships for a and b, as well as the pin test, can beapplied to select a and b. It will be found that with the four pickupspositioned thus far, tangential travel near the outside boundary willpresent no contact problem. Tangential travel near the inside boundary,however, may give rise to marginal situations; and the fifth pickup 45is provided which will remedy this situation.

The fifth pickup 45 will not only alleviate the problems cited above butif properly placed it will supplement the four other pickups so that thegeneral criterion for continuous current flow is met. The dimension dcan be determined experimentally, for example, as follows: The pickups41 through 44 are appropriately marked on translucent graph paper whosedimensions are that of the car chassis, which is laid over a segmentpattern drawing of actual size. Starting at one boundary andsuccessively working (radially) towards the opposite boundary, the pintest is applied and pickup 45 is positioned such that the pickuparrangement will meet the continuous current flow requirement.

For optimum operation, it is essential that proper spacing of contacts41, 42, 43, 44 and 45 is maintained at all times. A contact guard 46,shown in FIGS. 6 and 7, may be provided which will maintain the spacingof flexibly suspended contacts regardless of the movement of thecontacts relative to the track surface. The guard is constructed ofinsulating material extending below the vehicles frame 48 and havingholes therein corresponding to the spacing of the contacts 41, 42, 43,44 and 45. The guard allows the contacts to protrude slightly to contactthe track while at the same time constraining the contacts to thespecified five contact configuration. The guard 46 also serves toprevent damage to contacts during handling of the vehicle off of thetrack.

With reference to FIGS. 8-12, the basic control circuitry of the vehiclewill be described. The vehicles receiving circuitry generally shown inFIG. 8 at 50 is shown in functional block diagrams in FIG. 9. In thepreferred embodiment, the receiving circuitry consists of two channels,each furnishing a remotely controllable output voltage that drives atransducer such as an electric motor. The circuit channels areelectrically independent from one another, but their combined actionseffect simultaneous speed and steering control. The receiving circuitrymay be made responsive to either a pair of control signals, each ofwhich with fixed frequency and modulated in amplitude, or to a singlecontrol signal which is modulated in frequency as well as in amplitude.The former case is referred to as constant frequency operation, thelatter as variable frequency operation.

In constant frequency operation, each control function has apredetermined frequency 51 and 53 shown in FIG. 10 provided by anexternal controller (not shown). The receiving circuit 50 has two seriesresonant filters shown at 52 and 54in FIG. 8 and shown enlarged in FIG.11. Each filter is similar to filter 52 which has a capacitor 56 andinductor 58 selected in value to resonate at the predetermined frequency51, for example, and has a characteristic response curve approximatelyas in 60. Signals of the frequency 51 are present at the filters output62 with maximum amplitude, the voltage across the inductor 58 attainingmany times the amplitude of that of the signal across input terminals 64and 66. Signals at the input having frequencies other than the centerfrequency 51 are attenuated, relative to the center frequency, accordingto the frequency-voltage relationship prescribed by the filter responsecurve 60. Variations, due to modulation, of the input signal amplitudewill be present in the output voltage at 62 and are utilized, afterdetection and suitable amplification, to drive the transducer 82 at theoutput 120 of channel 81.

A similar output of frequency 53 is obtained, at 82, from the filter 54.This signal is processed in channel 83 and drives transducer 84. Thesimultaneous actions of transducers 82 and 84 effect steering and speedcontrolof the vehicle.

The use of series-resonant frequency filters 52 and 54 provides, inaddition to the voltage gain cited above, the following advantages notreadily obtainable with other types of filters of comparable simplicity:(a) Loading of the external driving source by the low impedance of eachfilter at its resonant frequency compresses the dynamic signal range. Inconsequence, for a given maximum dynamic range, many more controlfrequencies can be simultaneously employed, that is, superimposed in thedriving source, making possible the simultaneous operation of severalvehicles. (b) The source loading minimizes cross-coupling of any givencontrol signal into nonassociated frequency filters, thereby minimizinginterference to the operation of individual circuit channels. (c) Thesource loading results in relatively small A.C. signal excursionssuperposed on the direct voltage at branch 94 that supplies thetransistor collector currents, obviating the need for A.C. filtering inthat branch. (d) The source loading and restriction of dynamic signalrange tend to minimize spurious radiation of the control signals by theconductors comprising the feedwires to the track and the conductivetrack elements. (e) The seriesconnected L-C filters make possible thesimplest method of separating the DC. component from the control signalsat node 90, if the output is taken across the inductive element 58 as inFIG. 11.

FIGS. 12a and 12b show the frequency range assignment for constantfrequency operation where four vehicles or cars are to be controlled.The frequencies 51 and 53 are separated by khz for example. FIG. 12ashows an impractical assignment. Since the higher frequency assigned tocar 2 is 40 khz, it is the second harmonic of the lower frequency khzassigned to car 1, and there may be sufficient power in the secondharmonic of the 20 khz signal to interfere with car 2s performance. FIG.12b shows a practical assignment having the pairs of frequencies spacedat 30 khz intervals to avoid the problem of interference by controlsignal harmonics.

For the variable frequency operation the receiving circuit 50 remainsunchanged except for the tuning of the frequency filters. The singlecontrol signal now has the center frequency 68 positioned as shown inFIG. 13. This frequency can be varied by the external controller (notshown) between frequencies 70 and 72. The series-connected L-C filters52 and 54 now perform as slope detectors which are tuned to frequencies74 and 76 respectively, with overlapping characteristic response curves78 and 80. In the event that the amplitude of the control signal remainsconstant (for constant speed operation), as the signal frequencyapproaches for example frequency 74 because of a corresponding steeringcommand, the output 62 of detector 52 increases as prescribed by theresponse curve 78. Simultaneously, the output 82 of detector 54decreases as prescribed by the response curve 80. Amplitude variationsimposed (externally) on the control signal due to variable speedoperation will also appear at the detector outputs 62 and 82, superposedon the steering related amplitude variations.

Frequency assignment is determined by the frequency range between and 72and the power in the sidebands for that bandwidth. If 70 and 72 are 5khz apart for example, FIG. 12c shows a practical assignment with thecenter or carrier frequencies spaced 30 khz at 20 khz, 50 khz, 8O khz,and 110 khz.

With reference to FIG. 9, the vehicles receiving circuit is shown inblock diagram with channels 81 and 83. The control signals and D.C.power are picked up from the track and properly polarized by commutatingdiodes. The frequency filters isolate the A.C. control signals of thedesignated frequency from the DC. component, and attenuate all othercontrol frequencies. The DC. thus decoupled is connected to the poweramplifiers for driving the DC motors 82 and 84. The A.C. signal levels,or modulations, are recovered by diode detectors and control the poweramplifiers and thus the amount of drive voltage imposed on the DC.motors 82 and 84.

In FIG. 8, the five contacts 41-45 are shown connected to commutatingdiodes generally at 86. The signals once picked up from the trackthrough the contacts 41-45, properly polarized by the commutating diodes86 are presented at inputs 64 being positive and 66 being negative. Aresistor 88 in parallel with the filters 52 and 54 provides a minimumD.C. load for the commutating diodes 86 thus assuring that there isalways a low impedance path available for A.C. control signals even atinitial start up when only small currents are flowing. This assuressmooth initial acceleration.

The following description of channel 81 applies likewise to channel 83.The control signals and DC. component are isolated from each other atcircuit node 90. The capacitor 56 of filter 52 blocks the DC. component,permitting only the A.C. control signal to flow through the filter. Thecomposite signal flows into branch 94 where the DC component suppliesthe transistor collector currents. The A.C. control signal of afrequency identical with the resonant frequency of filter 52 is takenoff the filter output 62. The filter performs the functions ofselection, amplification, etc. described previously.

A level detector generally at 96 comprising a diode 98, a resistor 100and a capacitor 102 detects the voltage level of the unattenuatedcontrol signal of frequency 51 present at output 62 of filter 52. Analternate detector shown in FIG. 14 at 104 comprising additionally asecond capacitor 106 and a second diode I08, commonly called a voltagedoubler, may be used as a level detector. Both detectors 96 and 104 havean output 110 connected to the base of transistor 112. The signalpresent at detector output 110 in the case of detector 96 is a DC.voltage, resulting from half wave rectifying and filtering the output 62of filter 52. This DC. voltage at detector output 110 is thereforeproportional to the voltage at filter output 62 which is in turnproportional to the amplitude of the control signal of frequency 51. Inthe case of detector 104 the signal at output 110 is a DC voltage doublethat for detector 96 which may be useful if a larger drive signal forthe power amplifier is required.

The transistors 112 and 114 and resistors 116 and 118 comprise a twostage emitter follower power amplifier. The DC. voltage proportional tothe control signal present at output 110 is presented at output 120 lessonly the constant base to emitter junction voltage drops for eachtransistor 112 and 116. The DC. current available at 120 is sufficientto provide drive for the motor 82 limited by the voltage drop across themotor. The capacitor 122 filters out noise spikes generated by thecommutating brushes of the motor 82. Thus it can be observed that for agiven control voltage at output 120, corresponding to a particularcontrol signal at inputs 6 1 and 66, the transistor 114 will provide anyamount of current up to the limitations of its current carryingcapabilities or when properly designed up to the limit of the I R dropof the motor 62 when at a rest. As DC. motor 82 speeds up it developsback emf, which tends to reduce the current required. Thus, over theoperating range the transistor 114 and resistor 118 act as a voltagesource thereby utilizing self-regulating current characteristics of theDC. motor 82.

The receiving circuit 81 in FIG. 6 may be employed in alternateembodiments, for example, one in which steering and speed control arenot achieved through the cooperative action of the transducers 82 and8 1. The action of the two fixed frequency control signals and thecircuit channels would be entirely unrelated and independent: Thecontrol signal 51, for example, would uniquely control the vehiclespeed, with motor 82 supplying the motive power; the control signal 53would then uniquely control the vehicle steering via transducer 84which, in this case, could be a motor actuating a steering mechanism forthe unpowered (front) wheels, or it could be a solenoid or similardevice which again would so actuate a steering mechanism.

More generally, the circuitry 81 will furnish, in response to a suitableinput signal or signals, output voltages which are related to the inputas prescribed by the transfer characteristic of circuitry 81 and whichcan be used to drive a device or devices such as transducers in acooperative manner in the case of a single variable frequency inputsignal, or in an independent or cooperative manner in the case of twofixed frequency input signals.

With reference to FIG. and FIG. 16, one modification to the receivingcircuit 50 is shown in block diagram form and schematically to providedynamic braking and reversing or other similar control functions as forexample sounding a horn, turning on and off lights, etc. Reversing andbraking is accomplished by using a stepping relay 124 to reverse thepolarity of current in the DC. motors 82 and 8 1. The modification tocircuit 50 comprises a differentiator 126, a monostable multivibrator ora one shot 128, a line isolation filter 130, and the stepping relay 124.The reversing circuit 131 is connected to circuit 50 at point 116 or thesame point 132 on channel 83 if desired. Connections to input lines 64and 66 and to circuit 511 are indicated. The relay contacts areconnected to points 1211, 133 and 66 as indicated.

The external controller sends out a burst of several cycles of thefrequency 51, for example. The result is a pulse present at the output110. The pulse is differentiated into a spike which then triggers theone-shot 128 which in turn drives the stepping relay 1241.

The differentiator 126 comprising capacitor 134, and resistor 136provides only a positive spike since the negative spike is clamped bydiode 138. The monostable multivibrator comprises transistors 1411 and142, biasing resistors 144 and 146, feedback current limiting resistor148, dynamic feedback capacitor 150, collector current limiting resistor152, damping resistor 154, and coil load 156. Initially transistor 142is on and transistor is off due to biasing resistor 146 providingcurrent to the base of transistor 142 and biasing resistor 1 holding thebase of transistor 140 at ground. When the pulse spike from thedifferentiator 126 appears at node 158, transistor 140 begins conductingand current flows through coil 156 to activate the relay mechanism 124.Simultaneously the collector of transistor M11 goes to essentiallyground potential. The voltage change at the collector of transistor 140is coupled directly through capacitor 156 to the base of transistor 162,thereby causing it to cease conducting. The voltage at the collector oftransistor 162 rises and the voltage thus raised is fed back throughresistor 143 to the base of transistor 140 and maintains transistor 140in the conducting state. This state continues until capacitor chargesthrough resistor 146 and the dynamic feedback is broken to allow thetransistors to return to their initial state thereby terminating theactivation pulse in coil 156. The filter 130 provides transientprotection to the circuit when the car is first placed on the energizedtrack. Lamp is provided to indicate the status of the reversing relay124. Resistor 154 damps out any reverse voltage spikes appearing acrosscoil 156.

With reference to FIGS. 1'7 and 18 another modification to the receivingcircuit 50 is shown. Again a stepping relay 124 is used to reverse motorpolarity and a lamp 160 indicates the status. The modification tocircuit 511 comprises a high pass filter 162, a rectifier 163 and filter164, and a transistor switch 166. The reversing circuit 167 is connectedto circuit 50 at input lines 64 and 66 and at node 110 or 132 ifdesired. The relay contacts are connected to points 120, 133 and 66 asindicated.

The external control sends out .a slowly modulating sine wave on thecarrier frequency 51, for example. The low frequency sine wave detectedand present at point 110 is then filtered to remove the lowerfrequencies associated with change in speed or steering by high passfilter 162 comprising capacitor 168 and resistor 1711. The thus filteredsine wave is rectified by diode 163 and filtered to a smooth D.C. levelby filter 164 comprising capacitor 172 and resistor 174-. The DC. levelpresent across filter 164 is imposed on the base of transistor 176causing it to conduct and raising the voltage drop across resistor 178which in turn causes the voltage on the base of transistor 180 toincrease and thereby causes transistor 180 to conduct. When transistor1811 conducts current flows in coil 156 thereby activating the relaymechanism 124. Resistor 156 damps out reverse voltage spikes appearingacross the coil. Transistor 1811 continues conducting until the slowlymodulating signal ceases.

It will be noted that in the circuits in FIGS. 8, 16, 16 and 111transistors of the NPN type are used throughout, which choice isessentially arbitrary. Transistors of the PNP type may instead beemployed, which requires only the reversal of all diodes in therespective circuits. Instead of discrete components (transistors,diodes, resistors). integrated circuit devices may be employed whichincorporate most of the circuit in a single component.

It is claimed:

l. A track defining a roadbed and having continuous conductors arrangedto define spaced, transverse conducting segments of alternate oppositepolarity and strips of insulating material positioned between saidconducting segments, said conducting segments being adapted to receivesuperimposed alternating and direct current signals from an externalcontroller means, said track including a plurality of interchangeablesections mechanically and electrically engaged to form a closed roadbedconfiguration, the opposite ends of each section having complementaryconstruction so that the one end of any section can be connected to theother end of any other section without interrupting the electricalcontinuity of said conductors, said one end of each section terminatingalong the edge of one transverse conductor segment and said other end ofeach section terminating along the edge of said insulating material thatis positioned against the other transverse conducting segment.

2. A track as is defined by claim 1, wherein one of said sections issubstantially rectangular in shape.

3. A track as is defined by claim 1, wherein one of said sections issubstantially arc-like in shape with said continuous conductors arrangedto define radially extending conducting segments of alternate oppositepolarity, said radially extending conducting segments increasing inwidth proportionally to the radial distance from the center of a circledefined by said arc-like shape of said section.

1. A track defining a roadbed and having continuous conductors arrangedto define spaced, transverse conducting segments of alternate oppositepolarity and strips of insulating material positioned between saidconducting segments, said conducting segments being adapted to receivesuperimposed alternating and direct current signals from an externalcontroller means, said track including a plurality of interchangeablesections mechanically and electrically engaged to form a closed roadbedconfiguration, the opposite ends of each section having complementaryconstructIon so that the one end of any section can be connected to theother end of any other section without interrupting the electricalcontinuity of said conductors, said one end of each section terminatingalong the edge of one transverse conductor segment and said other end ofeach section terminating along the edge of said insulating material thatis positioned against the other transverse conducting segment.
 2. Atrack as is defined by claim 1, wherein one of said sections issubstantially rectangular in shape.
 3. A track as is defined by claim 1,wherein one of said sections is substantially arc-like in shape withsaid continuous conductors arranged to define radially extendingconducting segments of alternate opposite polarity, said radiallyextending conducting segments increasing in width proportionally to theradial distance from the center of a circle defined by said arc-likeshape of said section.